Novel features for time series analysis: a complex networks approach

Data Mining and Knowledge Discovery - Being able to capture the characteristics of a time series with a feature vector is a very important task with a multitude of applications, such as...     

Cadmium(II) removal from aqueous solution using microporous titanosilicate ETS-10

In this work, the removal of Cd²⁺ ions from aqueous solution using microporous titanosilicate ETS-10 was investigated in order to assess its potential as decontaminating agent in tertiary treatments. Accordingly, batch stirred tank experiments were carried out to study the ion exchange kinetics and equilibrium. Results show that pH affects considerably the ion exchange capability of ETS-10: at pH 4 it is 1.567 × 10² eq m⁻³, at pH 6 it is 3.629 × 10³, and no further increment was observed at pH 8. This is an extremely important observation since pH of industrial effluents and other wastewaters rounds 6. Both Langmuir and Langmuir–Freundlich isotherms were fitted to the experimental data measured. The second model performs slightly better as the calculated absolute average deviations show: AAD_L = 2.94% and AAD_LF = 2.40%. Concerning the kinetic behavior, the ion exchange was successfully represented by a Nernst–Planck based model (AAD = 11.9%).     

Components of a Variance Model for the Analysis of Repeated Measurements in Fixed-Point Comparisons

Experimental design is a statistical tool concerned with the planning of experiments to obtain the maximum amount of information from the available resources. This tool may be applied to metrology, especially for the analysis of a large number of repeated measurements (replicates) of short-term repeatability and the medium-term and long-term reproducibilities, enabling the inclusion of these “time-dependent sources of variability” in the uncertainty budget. The realization of the International Temperature Scale of 1990 (ITS-90) scale requires that laboratories usually have more than one cell for each fixed point, for comparison on a regular basis. The calculation of the uncertainty of such comparisons is considered here, taking into account these time-dependent sources of variability. These components of the uncertainty evaluated by a Type A method are obtained by the statistical analysis of the experimental results using the components of a variance model for designs consisting of nested or hierarchical sequences of measurements, as foreseen by the mainstream GUM. An application example of a balanced nested structure in the comparison of two fixed-point cells is presented.     

Choline- versus imidazole-based ionic liquids as functional ingredients in topical delivery systems: cytotoxicity,solubility, and skin permeation studies

Background: Poor drug solubility represents a problem for the development of topical formulations. Since ionic liquids (ILs) can be placed in either lipophilic or hydrophilic solutions, they may be advantageous vehicles in such delivery systems. Nonetheless, it is vital to determine their usefulness when used at concentrations were cell viability is maintained, which was considered herein.

Method: Five different ILs were prepared—three imidazole-based ILs: [C2mim][Br], [C4mim][Br], and [C6mim][Br]; and two choline-based ILs: [Cho][Phe] and [Cho][Glu]. Their cytotoxicity in human keratinocytes (HaCat cells), their influence in drug solubility and in percutaneous permeation, using pig skin membranes, was evaluated.

Results: Caffeine and salicylic acid were used as model actives. Choline-based ILs proved to be more suitable as functional ingredients, since they showed higher impact on drug solubility and a lower cytotoxicity. The major solubility enhancement was observed for caffeine and further solubility studies were carried out with this active in several concentrations of the choline-based ILs (0.1; 0.2; 0.5; 1.0; 3.0 and 5.0%, w/w) at 25?°C and 32?°C. Solubility was greatly influenced by concentrations up to 0.5%. The choline-based ILs showed no significant impact on the skin permeation, for both actives. The size of the imidazole-based ILs alkyl chain enhances the caffeine solubility and permeation, but also the ILs cytotoxicity. Stable O/W emulsions and gels were prepared containing the less toxic choline-based ILs and caffeine.

Conclusions: Our results indicate that the choline-based ILs were effective functional ingredients, since, when used at nontoxic concentrations, they allowed a higher drug loading, while maintaining the stability of the formulations.     

Mercury cycling between the water column and surface sediments in a contaminated area

Mercury cycling in the water column and upper sediments of a contaminated area, the Largo do Laranjo, Aveiro (Portugal), was evaluated after determination of reactive and non-reactive mercury concentrations in the water column and pore waters of sediments, collected in several places of this bay. In the water column, reactive mercury concentrations varied between 10 and 37 pmol dm(-3), the highest values being observed near the mercury anthropogenic source. However, reactive mercury was a narrowly constrained fraction of the total mercury, making up only 4-16% of the total, showing evidence of the importance of dissolved organic matter on mercury transport. In sediments, higher concentrations of mercury were also determined near industrial discharges. Results indicate the existence of an equilibrium between solid and liquid phases, determined by solid sediment/pore water distribution coefficients. Much of the mercury present in the solid fraction is associated with organic matter (r=0.837) and iron oxyhydroxides (r=0.919), but as oxides begin to dissolve in reduced sediments and organic matter decays, the adsorbed mercury is released. In fact, the mercury concentrations in pore waters of those contaminated sediments largely exceeded the values determined in the water column. As molecular diffusion may contribute to the dissolved mercury distribution in the overlying water column, this phenomenon was evaluated. However, the pore waters of Largo do Laranjo do not enrich the water column substantially in terms of reactive and non-reactive mercury. In fact, pore waters can contribute only to 0.2% and 0.5% of the reactive and non-reactive mercury present in the water column, respectively, showing that as long as mercury is being incorporated in sediments, it stays in stable forms.     

Spatial distribution of total Hg in urban soils from an Atlantic coastal city (Aveiro, Portugal)

The aim of this study was to investigate the levels and the spatial distribution of total Hg concentrations in soils from the urban area of Aveiro (Portugal) in order to assess the impact of industrial activities and identified Hg emission sources in these urban soils. For this purpose, soils were collected in 25 sampling points (at two depths) within the urban perimeter and in places considered representative of the main green areas of the city. A median concentration of 0.091 mg kg(-1) (dry weight) was obtained, regardless the depth. Aveiro was considered a low polluted city in terms of total Hg and no direct effects of emissions of Hg from industrial activities nearby could be detected in these urban soils. Despite of the low values obtained, high variability (range of approximately 0.5 mg kg(-1)) was observed in the results. Such was considered to be related to characteristic features of soils in urban settings and to the behaviour of Hg in the urban environment.     

Alteration of apparent viscosity of irradiated pepper — a tool for semi-quantitative estimation of irradiation dose

The feasibility of using apparent viscosity (_a) as a method for detecting the occurrence of previous irradiation of pepper was studied. Apparent viscosity of heat-treated suspensions of white and black pepper, nonirradiated or irradiated with different doses of ionising radiation (), was measured under different shear rates. Results of previous research were therefore expanded and their usefulness examined; low shear rate conditions were found to be preferable for the detection and semi-quantitative evaluation of irradiation doses. The experimental methodology for semi-quantitative estimation was developed and its scope and limitations are presented.     

Chemical composition of rainwater at a coastal town on the southwest of Europe: what changes in 20 years?

Rainwater was collected at the Portuguese west coast between September 2008 and September 2009, and analysed for pH, conductivity, and Cl⁻, NO₃⁻, SO₄²⁻, and NH₄⁺ concentrations. Results of rainwater chemical composition were compared with those obtained at the same site between 1986 and 1989. In both collection periods rainwater was predominantly (≈ 80%) associated to oceanic air masses. The rainwater concentration of H⁺ was in the same range as twenty years ago. A clear decrease of non sea salt sulphate (NSS-SO₄²⁻) was observed in 2008-2009 relatively to 1986-1989, not only in samples with origin in central and northern Europe, but also in samples from Atlantic Ocean and Mediterranean. This decrease indicates that SO₂ emissions were reduced, which may be due to a lower content of sulphur in oil by-products. A decrease was also observed in NH₄⁺ concentration in 2008-2009. On the contrary an increase of NO₃⁻ concentration was observed for samples of all origins in 2008-2009 relatively to 1986-1989, which was particularly high (more than 3 fold) for samples with origin in Atlantic Ocean, suggesting the incorporation of this ion by rainout at the sampling site. The contribution of local sources is indeed suggested by the moderate negative correlation of NH₄⁺, NO₃⁻ and NSS-SO₄²⁻ with rainwater volume. The high increase of NO₃⁻ concentration can be attributed to the increase of local vehicular and industrial emissions in the sampling area.     

Salmonella cross-contamination in swine abattoirs in Portugal: Carcasses, meat and meat handlers

In this study the occurrence of Salmonella in swine, pork meat and meat handlers along with their clonal relatedness is evaluated at abattoir level. Samples from the lymph nodes, carcass surface and meat of 100 pigs and 45 meat handlers were collected in eight abattoirs (July 2007-August 2008). Salmonella isolates were serotyped and genotyped by pulsed-field gel electrophoresis (PFGE). From the pigs tested, 42 produced at least one positive sample. A relatively high frequency of Salmonella occurrence was found in the ileoceacal lymph node samples (26.0%), followed by carcass (16.0%) and meat samples (14.0%). However, ileoceacal lymph nodes that test positive for Salmonella are not found to be a predictor of positive test results further on in the process. Besides the slaughterhouse environment, meat handlers were identified as a possible source of subsequent contamination, with 9.3% of the sample testing positive. Diverse Salmonella enterica serotypes were detected, mainly S. Typhimurium and the monophasic variant S. 4,[5],12:i:-, but also S. Derby, S. Rissen, S. Mbandaka, S. London, S. Give, S. Enteritidis and S. Sandiego, in total corresponding to 17 PFGE types. Our results demonstrate that besides a high level of Salmonella swine contamination at pre-harvest level, slaughtering, dressing, cutting and deboning operations are contributing to the occurrence of clinically relevant clones (e.g. S. Typhimurium DT104 and S. 4,[5],12:i:-) in pork products. This study also highlights the possibility of an ongoing Salmonella community being spread by abattoir workers.